The invention relates to the use of 3-deazaadenosine (c3Ado) for the preparation of a medicament against vascular diseases or graft rejection, especially atherosclerosis and graft vasculopathy.
Adhesion of leukocytes to the endothelial cell layer and their subsequent migration into the vascular wall are believed to play a key role during the development of atherosclerotic lesions. Monocytes/macrophages and lymphocytes, for example, are ubiquitous at all stages of atherosclerotic plaque development and propagate the local inflammatory process. Furthermore, lipid-laden macrophages accumulate within the plaque, thereby leading to instability with consequent rupture, thrombosis and acute vessel closure (1-3).
It has been widely appreciated that the inhibition of leukocyte adhesion and migration may have protective effects on plaque development (4-6). Cellular adhesion and migration are mediated by various molecules of the selectin, integrin, and immunoglobulin superfamily, such as the adhesion molecules vascular cell adhesion molecule-1 (VCAM-1) and Intercellular adhesion molecule-1 (ICAM-1). Previous studies have demonstrated increased expression of VCAM-1 and ICAM-1 on the surface of endothelial and vascular smooth muscle cells of human plaques and in experimental models of atherosclerosis (7-13). A recent study on C57/BL6 mice with homozygous mutations for various adhesion molecules indicated that endothelial adhesion molecules are directly involved in the pathogenesis of atherosclerosis (14).
Adhesion of leukocytes to the vascular endothelium is also an early step in graft rejection, leading to the migration of inflammatory cells into underlying tissues. Endothelial cells contribute to adhesion by expressing several inducible cell surface molecules that bind various inflammatory cells. Together with MHC molecules, the adhesion molecules have an important role in T-cell activation. For inflammatory cell adhesion to activated endothelial cells at least three separate receptor/ligand pairs are involved: ICAM-1/LFA-1, VCAM-1/VLA-4, and E-selectin/sialyl Lewis X, and/or related carbohydrates on leukocytes.
Current models propose that members of the selectin gene family (E-, P-, and L-selectin) mediate the initial adhesive interactions, including leukocyte rolling, and that subsequent firm adhesion and diapedesis require activation-dependent engagement of integrins with their endothelial ligands and PECAM-1, respectively.
Several previous studies showed that VCAM-1, ICAM-1, P-selectin, and LFA-1 are extensively expressed on endothelial cells in rat heart allograft atherosclerosis. Treatment of animals with antibodies to VCAM-1, VLA-4, ICAM-1 and LFA-1 induced Immunosuppression and inhibited graft atherosclerosis. Also the administration of ICAM-1 antisense oligonucleotides led to immunosuppression. In contrast, in ICAM-deficient mice no prolongation of cardiac allograft survival could be detected, indicating that this protein is not alone responsible for the induction of rejection or graft vasculopathy.
3-Deazaadenosine (c3Ado), a structural analog of adenosine, is an anti-inflammatory drug that has been shown to inhibit monocyte chemotaxis and phagocytosis (15-18). Furthermore, there are data revealing that this adenosine analog reduces tumor necrosis factor-xcex1-induced macrophage adhesion to endothelial cells in vitro via the selective inhibition of ICAM-1 synthesis (19). The underlying molecular mechanisms have not yet been fully clarified. c3Ado inhibits cellular methylation of membrane phospholipids and suppresses adenosylhomocysteine hydrolase (20,21). However, it has been suggested that the biological actions of c3Ado are independent of these mechanisms (21-24).
Because of its anti-inflammatory properties, c3Ado has been studied in a clinical trial In patients with rheumatoid arthritis (19,25), and this drug will be tested in humans for its in vitro antiviral (HIV) activity (26). The drug has never been tested in animal models of vascular disease.
Surprisingly, it was found that c3Ado inhibits in vivo leukocyte adhesion and concomitant formation of atherosclerotic lesions via inhibition of the expression of endothelial cell adhesion molecules, such as VCAM-1 and ICAM-1, as demonstrated in female C57/BL6 mice. These animals are reproducibly susceptible to fatty lesion formation which closely resembles early atherosclerotic plaques detected in humans (27-31).
Further, it was found that c3Ado Inhibits graft rejection and graft atherosclerosis in transplanted hearts.
An aspect of the present invention is the use of 3-deazaadenosine or analogs thereof for the manufacture of a medicament for the prevention and/or treatment of vascular diseases or graft rejection.
A further aspect of the present invention is the use of 3-deazaadenosine and analogs thereof for the manufacture of a medicament for the prevention and/or treatment of diseases associated with the expression of adhesion molecules ICAM-1 and VCAM-1 in endothelial cells.
According to the present invention 3-deazaadenosine and analogs thereof can be used. Examples of such analogs are salts of 3-deazaadenosine and precursors of 3-deazaadonosine which can be degraded in the body under physiological conditions to give 3-deazaadenosine, e.g., 3-deazaadenosine. phosphates. Further examples of analogs are deazanucleosides such as 3-deazaadenosine-3xe2x80x2-monophosphoric acid, 3-deazaadenosine-3xe2x80x2,5xe2x80x2-cyclophosphate and 3-deazaadenosine-5xe2x80x2-diphosphoric acid and salts and precursors thereof, respectively.
3-Deazaadenosine and analogs thereof are capable of preventing or delaying the occurrence of atherosclerosis. They prevent the appearance of fatty streak formation and all other stages of atherosclerotic plaque development in the intima of arterial blood vessels via inhibition of the expression of adhesion molecules in vascular endotheial cells. This leads to a reduction of adhesion and consecutive infiltration of monocytes into the subendothelial layer. Therefore the inhibition of the endothelial expression of VCAM-1 and ICAM-1 is the key mechanism, by which c3Ado inhibits atherosclerosis.
By the same mechanism c3Ado and analogs inhibit graft atherosclerosis in transplanted organs. Examples of transplanted organs are hearts, kidneys, livers, lung etc. The administration of 3-deazaadenosine and analogs thereof leads to reduced occlusion of blood vessels, particularly arterial blood vessels in transplanted organs. Furthermore, reduction of rejection of transplanted organs, for example, reduction of rejection of transplanted hearts is achieved.
Thus, c3Ado is suitable for the prevention and/or treatment of transplant vasculopathy.
Further preferred indications of 3-deazaadenosine and analogs thereof are prevention of rejection in xenotransplantation, prevention of restenosis after coronary interventions, especially after stent-implantation. Restenosis in stents (in-stent restenosis) can be prevented by coating the stent to be used with 3-deazaadenosine. The combination of covalent binding of 3-deazaadenosine to stents Is effective for the prevention of restenosis. Further preferred indications are prevention of reperfusion injuries, e.g., in the heart or in the lung, treatment and prevention of infectious and inflammatory coronary syndromes, prevention and treatment of dilated cardiormyopathy, prevention and treatment of viral myocarditis and prevention and treatment of infections by parasites such as Malaria tropica.
Another preferred indication is the use of 3-deazeadenosine and analogs thereof for reducing the level of homocysteine.
3-Deazaadenosine and analogs thereof can be used individually or in combination with other medicaments. When treating vascular diseases, for example, combination with cholesterol-reducing agents is conceivable. To prevent graft rejection 3-deazaadenosine and analogs thereof can be used in combination with immunosuppressive medicaments, e.g., cyclosporine. 3-Deazaadenosine and analogs thereof also can be combined with azathioprine, cortisone, rapamycine, tacrolimus and other immunosuppressive drugs.
The medicament can be administered any way, e.g., parenterally by means of injection or orally. Oral administration, e.g., in the form of tablets, capsules etc. is preferred.
The dose administered depends on the kind and severity of the disease. Normally, the dose ranges between 0.1 to 500 mg/kg body weight per day, preferably between 1 to 200 mg/kg body weight per day. Administration can be effected over a short period of one or more days. However, administration is usually effected over a period of at least one week. The dose can be varied during the administration period, if necessary.
A further aspect of the invention is a method of treating or preventing vascular diseases or graft rejection, comprising administering to a subject in need thereof, e.g., a human, an efficient amount of 3-deazaadenosine or an analog thereof.
Yet a further aspect of the invention is a method of treating or preventing diseases associated with expression of adhesion molecules ICAM-1 and VCAM-1 in endothelial cells comprising administering to a subject in need thereof, e.g., a human, an efficient amount of 3-deazaadenosine or an analog thereof.